In order to meet the increasing demand for wireless data traffic since the commercialization of 4th generation (4G) communication systems, the development focus is on the 5th generation (5G) or pre-5G communication system. For this reason, the 5G or pre-5G communication system is called a beyond 4G network communication system or post long-term evolution (LTE) system.
Implementation of the 5G communication system in millimeter wave (mmWave) frequency bands (e.g., 60 GHz bands) is being considered to accomplish higher data rates. In order to increase the propagation distance by mitigating propagation loss in the 5G communication system, discussions are underway about various techniques such as beamforming, massive multiple-input multiple output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large-scale antenna.
Also, in order to enhance network performance of the 5G communication system, developments are underway of various techniques such as evolved small cell, advanced small cell, cloud radio access network (RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), and interference cancellation.
Furthermore, the ongoing research includes the use of hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) {FQAM} and sliding window superposition coding (SWSC) as advanced coding modulation (ACM), filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA).
With the rapid advance of wireless communication technology, the communication systems have evolved to the 4th Generation mobile communication systems represented by the LTE system. The LTE system employs several key technologies to meet the ever-increasing traffic demand, and carrier aggregation is one of such technologies. Carrier aggregation is a technology to increase the data rate between a terminal (hereinafter, referred to as User Equipment or UE) and a base station (hereinafter, referred to as evolved Node B or eNB) in such a way of using one or more secondary carriers in addition to a primary carrier, unlike the use of a single carrier in the legacy communication technology, the data rate increasing in proportion to the number of carriers. In LTE, the primary and secondary carriers are referred to as primary cell (PCell) and secondary cell (SCell), respectively.
Meanwhile, in the case of using the carrier aggregation technology in uplink, the difference in frequency-specific propagation characteristics and difference in antennas are likely to cause differences in carrier-specific pathloss, channel conditions, and reception signal quality at the base station. There is therefore a need of a method for allocating resources, controlling power, and distributing traffic efficiently in adaptation to carrier-specific channel conditions to improve resource utilization efficiency and the uplink data rate of a terminal.